I've done some work on this, and wrote a draft paper <
https://github.com/chorman0773/CXX-Papers/blob/master/std_error_function.md
>.
I am interested in any feedback.
I decided on a similar function, std::compiler_error, which has the same
compile time behavior, but its UB at runtime. This would allow users to
write std::error, with whatever runtime behavior they wish.
I would be interested in any feedback people have, both on the semantics,
and in the structure of the paper itself.
Thank you to the great people on the std-proposals mailing list.

On Fri, 6 Mar 2020 at 11:07, connor horman <chorman64_at_[hidden]> wrote:

> constinit won't downgrade (as the standard requires a constant expression
> initializer). I did forget about that.
>
> On Fri, 6 Mar 2020 at 10:13, Thiago Macieira via Std-Proposals <
> std-proposals_at_[hidden]> wrote:
>
>> On Friday, 6 March 2020 06:46:56 PST connor horman via Std-Proposals
>> wrote:
>> > Currently it is not possible to implement std::error in a way that it
>> will
>> > work with initializing non-constexpr variables. Throwing an exception
>> > simply downgrades to runtime, only erroring if the result is needed at
>> > compile time.
>>
>> Does that also apply to constinit variables?
>>
>> --
>> Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
>> Software Architect - Intel System Software Products
>>
>>
>>
>> --
>> Std-Proposals mailing list
>> Std-Proposals_at_[hidden]
>> https://lists.isocpp.org/mailman/listinfo.cgi/std-proposals
>>
>